The present invention relates to a dual-rod cigarette manufacturing machine and, in particular, to devices used on such machines for shaving streams of shredded tobacco for forming, after wrapping, continuous cigarette rods.
The machine described in U.S. Pat. No. 4,336,812 of G.D. S.p.A., is designed to form two streams or layers of tobacco by accumulating single tobacco particles underneath respective supports consisting of parallel-moving suction conveyor belts.
Each stream of tobacco, as it is carried on its respective conveyor belt to cigarette forming means, is subjected to a shaving operation for ensuring essentially constant height and thickness of the stream. On single-rod cigarette manufacturing machines, the means employed for this purpose, known as shavers, consist of two identical, coplanar discs mounted on vertical, counter-rotating axes, the discs having cutting edges and being tangent with each other along the course of the tobacco stream.
Insufficient space is available for assembling the aforementioned shavers on dual-rod cigarette manufacturing machines on which the clearance between the two streams of tobacco, held on to their respective conveyor belts, is extremely limited and, being determined by specific construction requirements, not readily alterable. To be more precise, if a shaver of the aforementioned type were to be assigned to each of the two streams of tobacco, the disc located between the two conveyor belts would interfere with the course of the second stream, thus obstructing supply to the cigarette forming means.
For this reason, the shaving devices on dual-rod cigarette manufacturing machines, according to U.S. Pat. No. 4,304,243 of G.D. S.p.A., consist of pairs of identical, trucated-cone discs mounted on a slant and converging downwards.
The discs are arranged with the large-end cutting edges tangent and the generating lines aligned with the direction of the respective tobacco stream.
Consequently, the discs on each shaver are inclined downwards from the point of contact with their respective tobacco stream, thus eliminating any interference between the second stream and the disc facing it.
It has been found, however, that, over and above a given disc angle on the shaver, the tobacco stream encounters difficulty in working its way between the discs, with the result that it is only partly or unevenly shaved.